Photographic emulsion compositions and their preparation



United States Patent PHOTOGRAPHIC EMULSION COMPOSITIONS AND THEIR PREPARATION Ralph H. Talbot and Thomas J. McCleary, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey N0 Drawing. Application April 1, 1952, Serial No. 279,918

9 Claims. (Cl. 95-7) Our invention relates to photographic emulsions which employ ethyl cellulose phthalate as the carrier for the silver halide therein.

Since the earliest days of photography, research has been directed toward the discovery of suitable vehicles for the light-sensitive silver salts. Thus, collodion, which was originally employed for this purpose, gave way to the use of gelatin, which latter had the advantageous properties of being coatable from water solution and usable in dry form. Gelatin is susceptible to swelling in water or developers, and therefore permits processing. In view of the widely accepted use of gelatin as a-silver halide vehicle at the present time, the photographic industry has associated water permeability, and therefore Water sensitivity, with the emulsion layer, with the result that vehicles other than gelatin which have been proposed usually have properties similar to gelatin, particularly in being susceptible to swelling by water and to processing in aqueous solutions.

Gelatin has, however, exhibited properties which have been regarded as undesirable under certain circumstances. For instance, gelatin absorbs moisture readily when in an atmosphere having a high relative humidity, and, as a result, may thereby become soft and tacky. Also, under warm, moist conditions, gelatin is subject to the action of mold growth which has a derogatory effect upon the photographic image which may be formed by the emulsion. Gelatin, when subjected to an atmosphere of low relative humidity, loses moisture to the air and becomes dry and brittle. This loss and gain in moisture may contribute to curling of the film holding a gelatin layer due to changes in its moisture content from one time to another.

One object of our invention is to provide a vehicle for silver halide which will be free of the disadvantages which characterize the use of gelatin for that purpose. Another object of our invention is to provide a vehicle for silver halide in photographic emulsions in which the silver halide may be subjected to processing by developing and fixing solutions to good effect. A further object of our invention is to provide a vehicle for silver halide in photographic emulsions, the properties of which permit rapid coating of the emulsion upon the support therefor, and the use of hot air for quickly setting and drying the photographic product. A still further object of our invention is to prepare photographic emulsions using ethyl cellulose phthalate as the carrier for the silver halide therein. Other objects of our invention will appear herein.

We have found that dispersed silver halide may be carried in aqueous solutions of ethyl cellulose phthalates, and the photographic emulsions prepared'therefrom are characterized by good flowability while cold, which emulsions, after coating, may be readily gelled or set by the application of heat thereto. We have found that the emulsion layers prepared using ethyl cellulose phthalate as the carrier, after exposure, are readily susceptible of processing in conventional developers and fixing solutions to give photographic products of good quality. We have also found that photographic films prepared using ethyl cellulose phthalate asthe carrier for the silver halide are re- "ice sistant to the effects of changing humidity conditions, and, as a result, the photographic material is not affected by organisms, nor is there any appreciable change in flexibility, nor any eifect on the curling characteristics on the film which is prepared therefrom.

The ethyl cellulosephthalate which is employedis in the form of its salt, such as the ammonium salt, the amine salt (either primary, secondary or tertiary), or, in some cases, in the form of the alkali metal salts thereof. These emulsions are ordinarily prepared by mixing the. ethyl cellulose phthalate salt with the silver halide after it has been prepared in a peptizer so as to be in dispersed form. In some cases it may be desirable to mix the salt of ethyl cellulose phthalate with the peptized silver halide, and immediately coat the resulting composition upon the support. In other cases it may be desirable to mix the carrier with the peptized silver halide and coat either at the time or allow standing for a certain length of time. The silver halide grains may be prepared using any commonly employed peptizer therefor, as is Well known in the art. As a peptizer for the silver halide, the ethylenediamine salt of ethyl cellulose phthalate can be employed, and the emulsion may be prepared therefrom by mixing therewith as the carrier either more of the same type of salt with the silver halide dispersion so prepared or one of the other salts of ethyl cellulose phthalate. Another type of peptizer which has been found to be useful for preparing silver halide dispersions is the gelatin derivative type, such as phthalic anhydride derivatives of gelatin, as disclosed and claimed in U. S. Patent No. 2,525,753 of Yutzy and Frame, or gelatin derivatives as disclosed in U. S. Patent No. 2,614,928 of Yutzy and Frame. This peptizing material is compatible with ethyl cellulose phthalate salts and, upon mixing therewith, the resulting emulsion obtained may be allowed to remain in storage for any period desired. Other peptizers which may be employed in preparing the silver halide dispersions may be gelatin, oxidized protein derivatives or oxidized proteins as described in Lowe and Gates U. S. Patent No. 2,691,582 of October 12, 1954 or ethanol amine cellulose ester compounds. In cases where the peptizing material employed is not highly compatible with the ethyl cellulose phthalate salt, it is desirable that the coating operations take place very soon after the mixing of that carrier with the peptized silver halide dispersion.

In the coating of photographic emulsions in accordance with our invention, the emulsion is at a temperature lower than that to which the coating is subjected after it has been applied to the support therefor. For instance, the cellulose ether phthalate salts as employed in our invention are water-soluble, but insoluble in water at elevated temperatures, the solution temperature depending upon the particular cellulose ether phthalate employed. Therefore, it is preferred to dissolve the cellulose ether phthalate salt and prepare the photographic emulsion therefrom under cold conditions and, after coating, then apply a'higher temperature thereto, such as by the use of hot air, which immediately sets the coating. Our method of coating emulsions is especially useful in preparing photographic papers due to the fact that setting of the emulsion layer can be accomplished so rapidly that there is little, if any, penetration of the paper by the emulsion applied thereto. Consequently, papers without any preparatory coating can be employed as the support for emulsions applied in accordance with our invention. Emulsions in accordance with our invention can be coated upon glass, cellulose ester film support, paper, resin film support or any other material which is suitable as a support for a photographic layer.

The following is an example of the behavior of a typical cellulose ether phthalate useful in our invention: An ethyl cellulose, having an ethoxyl content of approximate- 1y. 45%,. was. phthalylated a cord ng. the method scribed in U. S. Patent No. 2,093,462 to give a cellulose ether phthalate having an apparent phthalyl content of 16.8%., This compound had, a viscosity, when made into a 3% solution in ethyl alcohol, (70%),, isopropyl alcohol (20%), n-butyl. alcohol of; 7.4: cps; 40' grams oi the dry cellulose etherphthalate was addedto 960- cc. of distilled water, and the slurry formed was cooled to 40 F. Ammonium hydroxide was added. drop-wise with stirring until solution was effected. The clear, filtered solution had apH of approximately 8.0. It was found that this. solution had itslowest viscosity at a temperature of 62 F. When the temperature isincreased, the viscosity of the solution rises: sharply, and shortly; beyond 665 F. the; solution sets; to a firm ge1.. This gel. can be. dried; in a strong current ofwarm air at 3.:dIY' and wet bulb temperature wherein the. wet bulb temperature is. at least the setting temperature of the; cellulose. ether phthalate. For example,v it may be convenient. to dry the gel at 100 dry bulb, and: 67 wet bulb temperature; If rapid: drying is desired, a dry'bulb temperature of 130i F. and. a wet bulb temperature of 80 F. can be employed. In the coating of: gelatin solutions: upon cellulose, ester film. base or the like, it, is customary to addwetting agents to; the solution to bring about an even wetting of the surface to be coated; In the case of the. salts ofcellulose ether phthalate, we have found, that the use of any wetting agent is unnecessary, as; the solutionsthemselvesreadily wet most surfaces, and, the coatings formed on the, film base show rem-arkable uniformity and freedom from, blistering or other effects often metwith in the; coating of gelatin emulsions on film base. Also, in the use of cellulose ether phthalate as the carrier for silver halide, the addition of hardeners is unnecessary, as. the vehicle in; its free acid state is. almost completely unafifected by water, either in thevapor or liquid form. If water of a basic character (hard water) isemployed, there may be conversion of some of the vehicle-,to-the form of a salt, which would render the ve hicle' more susceptible to the effect: of! water, particularly at low temperatures. In that case, prehardening: of the vehicle may be desirable.

In; the preparation of light-sensitive silver emulsions, it is customary to react silver nitrate with a: halide salt, such as potassium bromide, in, the. presence of a colloidalmaterial; It is often desirable to, removethe-excess ofi soluble saltspresent by meansof washing, Witha gelatin: vehicle, this-washing: is accomplished by setting the emulsion to a gel by chilling, forming noodles thereof and washing these-noodles incold water. This methodisislow; and costly, andsome silverand, gelatin.- are lost in the proceeding. In; the case of; a, cellulos ether plrthalate, emulsion, the noodling is. accomplished, by forcing a, thin: stream. of the liquid emulsionintodilute aqueous acid, such: as dilute acetic acid. The emulsion precipitates: in a thread-like formwhich is. susceptible tobeing: washed in. a stream of water of.- any desired temperature. Thexsoluble salts therein are thereby removed; without any lossoii silver: or cellulose ether phthalate. After this washing operation, the emulsion coating may be carriedout by chilling the washed noodles: of, emulsion, adding. a small amount of water containing dilute alkali, and; then adjusting theresulting solution to. give the correct, silver content and. viscosity. When the emulsion is free of bubbles,..itis ready forcoatmg.

In the coating of emulsions in. accordance with our invent-ion, there is; some slight. difference in, behavior, depending on the base used to formthe: salt. For instance, where the sodium salt of the cellulose ether phthalate is used, the emulsion layer, after drying, is water permeablev and remains so until. contact with an acid, and because; of this characteristic of the sodiumsalt of the cellulose ether phthalate, it is more desirable for use in preparing emulsions which are coated onto: paper, the car rier of the emulsions being wholly or partly the alkali metal salt of the cellulose ether phthalate. Inthe Case of the ammonium salt of the cellulose ether phthalatc, on the other hand, the drying operation in the coating of the emulsion layer liberates the, ammonia therefrom so that the free acid form of the cellulose ether phthalate is obtained. Thus, with a film base as the support, a dried film is obtained having an emulsion layer thereon which is no. longer water soluble... Because of thischaracteristic, ordinarily the; use of the ammonium salts: is; preferred for preparing emulsions to be used on film base. Although ethyl, cellulose phthalate is soluble, asa rule; in cold water having an alkaline pH, nevertheless emulsion layers in accordance with our invention can be processed in the conventional alkaline. developer solutions; without any undue softening or disintegration taking place. Also, emulsion layers in accordance with our invention are not susceptible to the effect of high humidities, nor do they support the growth of mold as characterizes gelatin emulsions. In addition, the emulsion layers. in accordance with our. invention show athigh degree of flexibility: over a wide humidity range, and there is no tendency to: cause curling as a result of changes of. humidity conditions.

In the development of emulsions using; acellulose ether phthalate vehicle, we have found that, although this vehicle is impervious. to. the action, of, neutral and acidic solutions, thisv material: is changed" by the alkali of a developer into. a water permeable material, and consequently upon. development the action onthe silver grains v proceeds at once and the development time is the same or even less than that off the same kind. of grains dispersed in gelatin. It is preferable in fixing emulsion layers according to our invention that a neutral. rather than an acid. hypo solution beemploycd-for this. purpose. After thedesired fixing'ha-sbeen. accomplished, the emulsion can then be immersed in aqueous. acid, such as dilute aqueous acetic acid, for a minute more or less to. convert the cellulose ether phthalate. to the water insensitive form. The moisture: content of the emulsion layer is appreciably reduced thereby, and after this treatment the film or paper containing the emulsion layer may be washed in water in. normal. fashion-i Due to the decrease of the moisture content. of; the emulsion in the acid bath, the; washed filrm is; so. nearly; dry that it, may be used for some purposes. after merely blotting off the surfacemoisture. As a negative, contact prints may. be made therefrom immediately withoutdamage to the emulsion layer. As an X-ray film, diagnosis can be made immediately after processing without the precau tions. ordinarily necessary in: the case ofi gelatin emulsions,

The temperature: at which photographic emulsions exhibit minimum viscosity; on, one hand, and; setting, on the; other,,varies from one cellulose:v ether'phthalate to the other. For instance,.,it maybe. stated a generality that the higher the etho-xyh content; the lower the: temperature necessary'to dissolve the cellulose ether phthalate, whereas the. higher the-phthalyl: content, the higher the temperature necessary for setting; the solution oi the ether, phthalate and the less: critical the setting temperature becomes. Also, the setting, point of the cellulose ether phthalate solution willvary'with the concentration thereof. For instance, with. atsolutionvv of 5% concentration, the; setting; point of a, given; cellulose; ether phthalate will be several, degrees; lower: than that of a solution of 3%; concentration. As a rule, it is preferred to operate-near'a ratio of 5: .1- cellulose ether phthalatc solution to concentrated silver halide dispersion when the cellulosev ether phthalate; is about 5%. concentration in water and the concentrated silver halide contains about 2% of peptizer with 1" molt of silver halide therein per liter of solution. It' is. desirable that suflicie-nt: ethyl cellulose phthalate; be employed as. a carrier for the silver halide: to obtain an emulsion coating-- onv a support of film orpaper when. the emulsion is' applied thereto so as to obtain a photographic product.

It is desirable that the cellulose ether phthalates-employed be prepared from ethylcellulose having an ethoxyl content of at least 42%. When a cellulose ether having an ethoxyl content of about 42% is used to prepare the cellulose ether phthalate, it is desirable that the ether phthalate contain at least 5% phthalyl, the preferred range for phthalyl content for a cellulose ether phthalate soprepared-being 8-15 When a cellulose ether having an ethoxyl content of 47.7% is used as the starting material, a phthalyl content of at least approximately 11% has been needed to get a product whose salts are soluble in cold water. We have found that the preferred range of phthalyl to impart to cellulose ethers of this type is within the range of 11l7%. When cellulose ethers having a still higher ethoxyl content, such as 49.5%, are used to prepare ether phthalates, few hydroxyl groups are present in the cellulose ether, and therefore the amount of phthalyl which can be incorporated is limited. In this case, 16.5% phthalyl is approximately the limit of phthalyl which can be incorporated, but at least approximately 12% of phthalyl should be imparted-for solubility of the ether phthalate salts in cold water. The cellulose ether phthalates employed may vary also as to viscosity. We have found that in the case of low viscosity esters, such as those whose salts have a viscosity of less than cps. in 4% solution in water, it is usually desirable to incorporate some plasticizer, such as triacetin or polyethylene glycol in the cellulose ether phthalate composition. In the case of higher viscosity esters, plasticizer is usually unnecessary.

In applying emulsion layers in accordance with our invention using cellulose ether phthalate, it is preferred that the layer have a thickness when dry of at least .00035 of an inch for cine positive film. With other types of photographic products, the emulsion layer has a dry thickness from .0001 to .001 inch or more. For applying on film base, it is desirable that that base be first subbed with a layer which promotes good adhesion. For instance, film base having a layer thereon of a mixture of cellulose nitrate and gelatin is useful for forming photographic products in accordance with our invention.

Instead of cellulose ether phthalate, some other dicarboxylic acid ester of the cellulose ether may be employed as the carrier for the silver halide in accordance with our invention, such as the succinate, the maleate or the like.

The following examples illustrate our invention:

Example 1 2 parts of starch acetate were dissolved in 30 parts of distilled water, warming gently. The solution was cooled to 40 F. and there was then added thereto simul taneously in slow streams and with vigorous stirring 10 parts of a silver nitrate solution and 10 parts of a solution of potassium bromide and iodide. The silver nitrate solution had been made by dissolving 100 grams of silver nitrate in 200 cc. of distilled water. The second solution had been made by dissolving 76 grams of potassium bromide and 2.4 grams of potassium iodide in 200 cc. of distilled water. The preparation of the silver halide and the remaining steps in this example were carried out under darkened conditions.

The resulting product which comprised grains of silver halide dispersed in the starch acetate solution was mixed with 50 parts of a 5% solution of the ammonium salt of ethyl cellulose phthalate, the temperatures of both solutions being at approximately 50 F. The cellulose ether phthalate employed was the result of phthalylating a cellulose ether having an ethoxyl content of 45% to a point that a phthalyl content of 19.8% was present therein. The suspension of silver grains in cellulose ether phthalate obtained was then forced through a small glass tube into dilute acetic acid, thus producing a thread-like precipitate of the acid form of the cellulose ether phthalate carrying the silver halide grams. Thisprecipitate was washed in a stainless steel wire basket with water until the wash water which resulted no longer gave a test for soluble halides. The precipitate was then partially dried and was mixed with parts of distilled water containing 1 part of starch acetate therein. The slurry thus obtained was cooled to 55 F., and sufiicient ammonium hydroxide was added thereto to convert the cellulose ether phthalate into the form of its phthalyl ammonium salt, thus resulting in dissolution of the silver halide emulsion. The emulsion was then spread upon a glass plate which had been subbed with gelatin, the plate was warmed to set the emulsion to a gel, and it was then transferred to a drying oven where the water was removed from the emulsion layer. The resulting photographic plate was exposed to a photographic negative, following which the plate was developed with a conventional developer, fixed in a neutral hypo fixing bath, treated with dilute aqueous acetic acid for a short time, washed and dried. A positive image of good quality was obtained.

Example 2 .5 part of a cellulose ether phthalate, which had been prepared by phthalylating ethyl cellulose having an ethoxyl content of 45% to a phthalyl content of 16.8%, was suspended in 34 parts of distilled water. The resulting suspension was cooled to 40 F., and, while agitating, ethylenediamine was added drop-Wise thereto until solution was effected. There was then added simultaneously to the solution, while vigorously agitating, 17 parts of a potassium bromide solution and 17 parts of a solution of silver nitrate, these solutions having been prepared in the manner described for the preparation of the corresponding solutions in Example 1. This mixture was stirred for 1 minute and there was then added with stirring 100 parts of a 4% solution of the ammonium salt of a cellulose ether phthalate of the same type as employed in the preceding example. The emulsion thus obtained was precipitated in thread-like form into dilute acetic acid, as described in Example 1, and the precipitate was washed with warm water, drained and dissolved in cold water made alkaline with NHiOH. The emulsion was diluted to give a readily flowable viscosity. The emulsion was then cooled to 50-55 and was coated on a subbed glass plate which had also been cooled. After coating, the glass plate was placed over a hot plate at and subjected to a current of warm air. The coating thereon dried and was exposed to a photographic negative and processed by means of developer, neutral hypo and dilute acid to give a positive image. All the steps of this example where protection of the silver halide was necessary were carried out under darkened conditions.

Example 3 A dispersion of silver halide was prepared as follows,

using as the peptizer a phthalic anhydride derivative of gelatin prepared by reacting 100 parts of gelatin with 5 parts of phthalic anhydride by the method described in Example 1 of the Yutzy and Frame U. S. Patent No. 2,525,753. The following solutions were prepared:

Solution B was run into agitated solution A over a period of 2 minutes. This step and the remaining steps of preparing and coating the emulsion were carried out under darkened conditions. The dispersion was cooled to 35 C., and there was added thereto 16% parts of 2 normal H2804 lowering the pH to 2.95. The mass was allowed to settle and was decanted. 400 parts of water were added to the coagulum which had been obtained, and the whole was stirred for 5 minutes at 40 C. at a pH of 4.1. The solid particles were again allowed to settle and separated from the liquid by decanting. The'solid material was then dispersed at 45' 6; with 215. normal;

NaGJH for- 35 minutes with. the pH adjusted to/ 614'; The final volume. was adjusted to SOO-pa-rts by addinglwater thereto. Also, there was added 0.009 part of allylethiourea in- 1 8 parts ofmethyl alcohol, andthe mass-was heated for 36 minutes at 65 C; It was thencooled to. 40 C, dispersed: with an equal volume of water andwas mixed with a solution of the, ammonium salt of a. cellulose ether phthalate using 5 parts of the ethyl cellulose phthalate solution. to 1' part of the silver halide dispersion, with the tempera ture of the dispersion 65 F., and that of 'the cellulose ether phthalatesolution 50 F. The cellulose ether phthalate employed was one which; had been prepared from an ethyl: cellulose having a 45 ethox-yl content-towhich had been imparted a phthalyl content of 1 4.3%. The emulsion was thoroughly mixed in acentrifugal mixer and was coated onto a conventional film base. The temperature of. the coating roll was 146 F. and of thechill' box 135 Fl, the coating having been carried outat a. rate. of 40 feet per minute. The emulsion layer was dried in a current of air, the dry bulb temperature thereof being 120' F. andthe wet bulb temperature being 75 F. A sample ofthe coated film was exposed onthe Ib sensitometer and processed 3 minutes in developer 13-19 with the following results:

/i Speed 0.84

Gamma 1.32

Fog 0.05

Example 4 A silver halide dispersion was prepared as described in Lowe and Gates,.Serial'No. 7 68,480, by a peptizing agent prepared by reacting upon casein at an. alkaline pH with acetic anhydride and acrylonitrile, whereby acetyl and acrylonitrile groups are introduced into the casein, followed by oxidizing the product with dilute hydrogen peroxide and" precipitating the oxidized casein derivative formed by adding acid to the mass to impart an acid pH, such as 4.3, thereto.

Solution A was prepared consisting of 250 parts of a 10% solution of the modified casein in water, 141 parts of potassium bromide, 1.3 parts ofpotassium iodide and 1500 parts of' water, all at a temperature of 60" C. and a pH. of 6.0. Solution B was prepared by mixing together 170 parts of silver nitrate and 1800 parts of water, this solution having a temperature of 62 C. Solution B was run into agitated solution A over a period of 10 minutes. The mass, was then cooled immediately to 35 C. at a pH' of 6.2. There was then added 16 /2 parts of 2 normal sulfuric acid which imparted. a pH of3, and the precipitate formed was allowed to settle and the liquid was decanted therefrom. There was then added 4000 parts of cold water, the grains were dispersed in the water with, stirring for 5 minutes, the. pH being 3.5, and then 1 part of 2.5 normal sodium hydroxide was added. The grains were allowed to settle and the. liquid was decanted off. 12 parts of 2.5 normal NaOH was then added, which raised the pH from 3.9. to 7.6. The grains were. dispersed for 35 minutes at 45 C. The pH was then adjusted to 7.5 with 2 normal sulfuric acid, and the final volume was adjusted to 1000 cc. of the dispersion permol of silver. The temperature was adjusted to 65 C. and 9 mg. of allyl thiourea permol of silver halide was stirred into the mass for 30 minutes at that temperature. The material was then cooled to- 50 F. and mixed with a 5% solution of; the ammonium salt of ethyl cellulose phthalate. This ethyl cellulose phthalateresulted from phthalylating a. cellulose ether having an ethoxyl content of 45% toa phthalyl content of 15.4%. The mixing was carried out in a centrifugal mixer in the ratio of 1 part of the silver halide dispersion to 5 parts of the solution of: ethyl cellulose ammonium phthalate, the mixed mass being at 50 F. The emulsion mixture; was then coated onto conventional film base support. as a thin layer, the coating roll and the chill box each having a temperature of; 140." E, thetcoating: operation beiuo a r cd out? at; therate 0t. 28 feet p.e1:-minute-.. 'Ihecoatedgfilnnwasathen drieclwith noun-enact" El'UlI8VlHQaLIQEHRQIZ3JtHIG of: 1g00 E. and a wet bulb temperature of 70; EL TlIQITQiWaSIthHS; obtained a photographic film of the negative: type. 'llhis: film was. adapted; for; exposure and: processing by-thc. use of conventional developer and fixing in. neutrala hyp followed by treatment: with aqueous; acid to: make; sur that the cellulose. ether phthalate, at this. stage is;in .the; acid form.

We. claim;

1.. A method of'preparing; photographic; productshaving; a; silvenhalide emulsion layer which; includes-the; steps of; preparing silver halide; in, a dispersing; agent therefor; forming therefrom; silver: halide photographic emulsion inwhich the silver halideis dispersed; an; aqueoussolup tion ofv a water-soluble-saltselected from the ammoniu alkali metal. and amine; salts, of the. phthalic, suceinic and rnaleic acid. esters of; ethyl cellulose: having an alkoxyl content or at least 42% which; esterr has; a. dicarboxylic acidradical content: of; at least 5%,, coating the emulsion thus; prepared onto, a support therefor; and immediately thereafter applying to! the emulsion; layer warm air having a wet bulb temperature of at. least the d setting temperature of the ethyl; cellulose ester? salt until setting of the emulsion layer obtained and continuing the application of thewarnr dry airto. the emulsion layer, until the layer has dried.

2.. A methodof preparing; photographic. products. having a silver halide emulsion. layer which includesthe steps of preparing silver halide in a dispersing agent therefor, forming therefrom a, silver halide photographic emulsion comprising-grains. of silver halide dispersed in anaqueous solution, of a water soluble salt. selected from the ammoniurm, alkali metal. and amine; salts of a phthalate of ethyl cellulose having an: alkox-yl'conteut. Ofiiat leastz42%v, the ester having a phthalyl content of at least 5%, coating the silver halide emulsion thus preparedontoa support therefor and immediately thereafter applying totheemulsion layerthus. formed warm air. havinga; wet bulhtem: perature of at least the setting temperature of the, ethyl cellulose phthalate salt until settingoii the emulsion layer is obtained and. continuing. the application'of warm, dry air to the emulsion layer untilthat layer has-dried.

3. A method of preparing. photographicproducts having a silver halide emulsion layer which includes; the steps of preparing silver halide in. an. aqueous solution of an ethylene diamine salt of ethyl cellulose phthalate as the dispersing agent, forming therefrom a silver halide photographic emulsion by mixing. he: silver halide dispersion. thusprepared: with an; aqueous; solution of an ammonium salt of a phtha-late off ethyl cellulose, having an alkoxyl content. of at least 42%, hfi. ster having a phthalyl content of at. least 5%,. as; the-vehicle for; the silver halide, coating the emulsion thus; prepared onto a support therefor and immediately thereafter applying t the emulsion layer thus: formed warm air haying a wet bulb temperature of at'least the; setting; temperature.- of the ethyl cellulose phthalate salt until-i settingof the; emulsion layer is obtained and continuing; the applicationof warm, dry air. to the emulsion layer until that layer'has dried.

4. A method of'preparing photographic products havinga silver halide emulsion layer which includes the steps of preparing silver halide. in an aqueous solution of :a starch acetateas the dispersing agent, forming therefrom a silver halide photographic emulsion by mixing-the; silver halide dispersion thus prepared with. an aqueoustsolution. ofan ammonitun salt of a phthal-ate of. ethylcellulose having an alkoxyl content, of at least 42%,, the; ester. havinga phthalyl content of at least 5%, as the vehicle for the silver halide, coating the-emulsion thus pre-paredi onto. a support. therefor and immediatelythereafterapplying to the emulsion. layer thusv formed. warnt air.- hatving a wet bulb temperature of at least thesetting; temperature of the ethyl cellulose phthalate salt until setting of the emulsion layer is obtained and continuing the application of warm, dry air to the emulsion layer until that layer has dried.

5. A method of preparing photographic products having a silver halide emulsion layer which includes the steps of preparing silver halide in an aqueous solution of a phthalic anhydride derivative of gelatin as the dispersing agent, forming therefrom a silver halide photographic emulsion by mixing the silver halide dispersion thus prepared with an aqueous solution of an ammonium salt of a phthalate of ethyl cellulose having an alkoxyl content of at least 42%, the ester having a phthalyl content of at least as the vehicle for the silver halide, coating the emulsion thus prepared onto a support therefor and immediately thereafter applying to the emulsion layer thus formed warm air having a wet bulb temperature of at least the setting temperature of the ethyl cellulose phthalate salt until setting of the emulsion layer is obtained and continuing the application of warm, dry air to the emulsion layer until that layer has dried.

6. A method of preparing photographic products having a silver halide emulsion layer which includes the steps of preparing silver halide in an aqueous solution of an oxidized casein derivative containing acetyl and acrylonitrile groups as the dispersing agent, forming therefrom a silver halide photographic emulsion by mixing the silver halide dispersion thus prepared with an aqueous solution of an ammonium salt of a phthalate of ethyl cellulose having an alkoxyl content of at least 42% the ester having a phthalyl content of at least 5%, as the vehicle for the silver halide, coating the emulsion thus prepared onto a support therefor and immediately thereafter applying to the emulsion layer thus formed warm air having a wet bulb temperature of at least the setting temperature of the ethyl cellulose phthalate salt until setting of the emulsion layer is obtained and continuing the application of warm, dry air to the emulsion layer until that layer has dried.

7. A photosensitive silver halide emulsion capable of setting in layer form when subjected to elevated temperature which comprises grains of silver halide dispersed in an aqueous solution of a water-soluble salt selected from the ammonium, alkali metal and amine salts of the phthalic, succinic and maleic acid esters of ethyl cellulose having an alkoxyl content of at least 42% which ester has a dicarboxylic acid radical content of at least 5% as the carrier for the silver halide grains.

8. A photosensitive silver halide emulsion capable of setting in layer form when subjected to an elevated temperature which comprises grains of silver halide dispersed in an aqueous solution of a water soluble salt, selected from the ammonium, alkali metal and amine salts, of a phthalate of an ethyl cellulose having an alkoxyl content of at least 42%, the ester having a phthalyl content of at least 5 as the carrier for the silver halide grains.

9. A photosensitive silver halide emulsion capable in layer form of setting at an elevated temperature which comprises grains of silver halide dispersed in an aqueous solution of an ammonium salt of a phthalate of ethyl cellulose having an alkoxyl content of approximately 45% the ester having a phthalyl content of approximately 19.8%, as the carrier for the silver halide grains.

References Cited in the file of this patent UNITED STATES PATENTS Malm et al Sept. 21, 1937 Sheppard et al Aug. 23, 1938 Stand et a1. Aug. 23, 1938 OTHER REFERENCES Photographic Emulsion (1929) American (Pages 166, 167 and Wall Photographic Publication Co. 

1. A METHOD OF PRAPARING PHOTGRAPHIC PRODUCTS HAVING A SILVER HALLIDE EMULSION LAYER WHICH INCLUDES THE STEPS OF PREPARING SILVER HALIDE IN A DISPERSING AGENT THEREOF, FORMING THEREFROM A SILVER HALIDE PHOTOGRAPHIC EMULSION IN WHICH THE SILVER HALIDE IS DISPERSED IN AN AQUEOUS SOLUTION OF A WATER-SOLUBLE SALT SELECTED FROM THE AMMONIUM, ALKALI METAL AND AMINE SALTS OF THE PHTHALIC, SUCCINIC AND MALEIC ACID ESTERS OF ETHYL CELLULOSE HAVING AN ALKOXY CONTENT OF AT LEAS 42% WHICH ESTER HAS A DICARBOXYLIC ACID RADICAL CONTENT OF AT LEAST 5%, COATING THE EMULSION THUS PREPARED ONTO A SUPPORT THEREFOR AND IMMEDIATELY THEREAFTER APPLYING TO THE EMULSION LAYER WARM AIR HAVING A WET BULB TEMPERATURE OF AT LEAST THE SETTING TEMPERATURE OF THE ETHYL CELLULOSE ESTER SALT UNTIL SETTING OF THE EMULSION LAYER IS OBTAINED AND CONTAINING THE APPLICATION OF THE WARM AIR TO THE EMULSION LAYER UNTIL THE LAYER HAS DRIED. 